Bagpipes are a class of free reed musical instrument, typically made up of an airtight bag, a blowpipe or elbow-worked bellows (by which the bag is inflated), one or more tunable drones which play continually with a constant sound (droning or skirling), and the chanter, which has holes that are covered or uncovered with the fingers, to create individual notes. The most complex of bagpipes, the Irish Uilleann pipes, have yet another set of pipes, called regulators, which play chords.
There are many kinds of bagpipe, but the best-known is the Great Highland Bagpipe, which was developed in Scotland and is played in countries around the world. It has two tenor drones, one bass drone, a blowpipe and a chanter. At the base of the blowpipe is a valve that allows air to flow into the bag, but not flow out. This helps keep the bag pressure steady, when the piper takes a breath. The drones, blowpipe and chanter fit into stocks: cylindrical, usually wooden tubes, that are tied into the bag. There are eight holes on the chanter that can be covered and uncovered to create the nine melody notes. Grace notes and more complex embellishments are an important part of the music for this kind of bagpipe.